The price of petrol for British motorists has continued to soar in reaction to the destruction caused by Hurricane Katrina - even though crude oil prices have now fallen back to their pre-storm levels.

A litre of unleaded yesterday reached an average price of 94.58p on Britsh forecourts, according to market research firm Catalist. That compares with 91.88p a litre on Thursday, and 89.63p a month ago.

Filling the 50-litre tank of a family car now costs £47.29 - an increase of more than 5.5 per cent compared with the same day in August.

Hurricane Katrina has knocked out refineries and pipelines along the Gulf of Mexico, an area that provides about one-third of the United States' fuel supplies. Wholesale fuel prices in the US, the world’s biggest energy consumer, rose 37 per cent last week as demand outstipped availability.

This has had a knock-on effect on European prices as supplies were diverted across the Atlantic.

Akber Ali, a researcher at Catalist, said the jump of more than 2p a litre since Thursday was "amazing," and the biggest single increase since the firm started monitoring prices in 1999. "We're used to prices ticking up in increments of 0.1p or 0.2p - we've never seen anything like it," he said.

While competition has discouraged some British operators from passing the full extent of wholesale price increases to their customers, petrol stations in many rural areas are already charging more than £1 a litre. Small operators, which are less able to spread costs across a network, are also lifting their forecourt prices at a faster rate than larger operators such as supermarkets.

The highest price recorded in Britain yesterday was 102.9p for a litre of unleaded, Mr Ali said. That price was recorded in eight of the 5000 petrol stations monitored by the firm.

Ray Holloway, director of the Petrol Retailers Association, said diesel was now almost certain to top the £1 mark. British drivers were yesterday paying an average of 97.27p for diesel, Catalist research shows; a month ago they were being charged 93.55p.

"We have a shortage of the product," he told the BBC. "Diesel motorists will be complaining about that and perhaps asking the Chancellor about the tax position."

Britain's poorest and the most-dependent rural families are now spending more than a quarter of their weekly income running a car because of petrol price increases, according to the RAC Foundation. It today called on the Government to make fuel tax variable in order to help low-income families cope with the cost.

Britain's higher pump prices have come despite crude-oil futures dropping from record levels in recent days. Hopes have grown that a fuel supply crisis will be averted after members of the International Energy Agency late last week opted to release oil from strategic reserves.

However, these extra supplies may not help ease the burden on drivers given the time they will take to arrive. Refining capacity for turning crude into petrol also remains extremely limited.

"The companies have no choice," said Mr Ali. "There's a two-to-three week lag between prices on the market and what we see charged at the stations, so we probably haven't have seen the end of these rises yet."

Brent crude for October delivery today lost $1.42 to $64.64 a barrel in London, while New York-traded oil futures closed on Friday at $67.57. Both contracts had reached record highs on Tuesday, hitting $68.89 and $70.85 respectively.

A poll of Times Online readers last week revealed 54 per cent of respondents think US-traded oil futures will top $90 a barrel. Just 17 per cent believe prices have already peaked at around the current levels.

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